Spring hinge for bifold doors

ABSTRACT

A spring hinge is provided for bifold doors such as are commonly used on closets. The hinge has an over-center spring action that closes the doors when they are nearly closed and opens the doors when they are nearly open and retains the doors in those positions respectively. A power pack having two pivotally interconnected U-shaped rigid members displaces the driving spring away from tne ends of the doors to provide clearance. In one embodiment the power pack connects to the respective hinge leaves by way of a bearing tooth on each hinge leaf and bearing faces on the rigid members of the power pack. The spring on the power pack between the rigid members acts to urge the bearing faces towards each other. A line between the bearing teeth lies on opposite sides of the hinge pivot axis when the hinge is in its open and closed positions, respectively. In one embodiment of power pack, the rigid members are formed of sheet metal and pivotally interconnected without a pin joint. In another embodiment the power pack is molded of plastic with an integral web between the rigid members forming the pivot. A pin type pivot may also be used between the power pack and the hinge leaves. The hinge leaves are corner connectors for doors having a thin panel, end rail and side stile.

i United States Patent U91 .1 erila 11 3,849,835 [451 Nov. 26, 19 74 1 1SPRING HINGE FOR BTFOLD DOORS [75 Inventor: Torsti T. T. Jerila, BaldwinPark,

Calif.

['73] Assignee: Acme General Corp., Monrovia,

Calif.

[22] Filed: Sept. 19, 1972 [21] Appl. No.: 290,401

521 U.s.'ci. 16/182 Primary Examiner-Paul R. Gilliam AssistantExaminer-William E. Lyddane Attorney, Agent, or Firm-Christie, Parker &Hale [5 7 ABSTRACT A spring hinge is provided for bifold doors such asare I v commonly used on closets. The hinge has an overcenter springaction that closes the doors when they are nearly closed and opens thedoors when they are nearly open and retains the doors in those positionsrespectively. A power pack having two pivotally interconnected U-shapedrigid members displaces the driving spring away from tne ends of thedoors to provide clearance. in one embodiment the power pack connects tothe respective hinge leaves by way of a bearing tooth on each hinge leafand bearing-faces on the rigid members of the power pack. The spring onthe power pack between the rigid members acts to urge the bearing facestowards each other. A line between the bearing teeth lies on oppositesides of the hinge pivot axis when the hinge is in its open and closedpositions, respectively. In one embodiment of power pack, the rigidmembers are formed of sheet metal and pivotally interconnected without apin joint. In another embodiment the power pack is molded of plasticwith an integral web between the rigid members forming the pivot. A pintype pivot may also be used between the power pack and the hinge leaves.The hinge leaves are corner connectors for doors having a thin panel,end rail and side stile.

37 Claims, 18 Drawing Figures PATENTLD 137261974 SHEET 5 BF 6 1 SPRINGHINGEYFOR' BIFOLD DOORS installation has four door panels with twomounted to swing towards each jamb. At each side one of the panelspivots relative to the jamb in substantially the same manner as anydoor. The second panel is mounted on hinges to the edge of the firstpanel and typically pivots in'the oppositedirection from the firstpanel. The far edge of the second panel is typically guided by tracks atthe top and'bottom of the door respectively so that the far edge travelswithin the door frame. Thus, when the bifold door is closed both thefirst and second panels are within the door frame and in alignment. Whenthe bifold door is opened the first panel pivots at the jamb and itsopposite edge moves out; the second panel pivots so that its faceapproaches the face of the first panel. The edges of the two doors wherethey are pivoted together also move out from the door frame. Thefurthest edge of I the second panel moves along the tracks towards thejamb.

, as 3/16 or A inch thick plywood, forming the main face of the door. Ametal stile is provided along each side edge of the panel and a metalrail is provided at the top and the bottom. A comer connector securesthe adja-- cent rail and stile together at each corner. Since hingescannot be secured to the 'panel in any practical manner, the comerconnectors on adjacent doors may be pivotally interconnected to form ahinge. Such hinge cannot extend any substantial distance beyond the endof the doors or it will interfere with the guide track. In addition, ahinge at the bottom of the door might become tangled with shag carpetingor the like It is desirable in a bifold closet door to have some meansfor assuring that the door stay closed, that is, that the two adjacentpanels are in substantial alignment. Preferably, this function is addedto the structure of the hinge and when associated with a cornerconnector issubject to the same constraint that it should not extendmuch beyond the end of the door. Connections between the edge stiles atsome point between the ends of the doors are generally not satisfactorysince the engagement of the stile with the panel is not suffficientlyuniform to assure good alignment in all installations.

It is therefore desirable to provide hinges for bifold doors that urgethe door towards a closed position and hence hold the panels inalignment. Such a hinge should be useful with thin panel doors havingperipheral stiles and rails. The hinge leaves should engage the doorwith sufficient rigidity to resist cave-in if the door is pushed in thewrong direction. It is also desirable that the hinge urge the doortowards its open position, particularly for retaining it in suchposition. Preferably such hinges are economically mass produced and aresimple to install.

BRIEF SUMMARY OF THE INVENTION opened position. Preferably the line ofapplication of spring force to the hinge leaves moves over center foralternatively urging the hinge towards its open position or closedposition. The spring power pack preferably engages the top of the hingeleaves by way of a window through each of the leaves and has its springlocated below the top of the hinge. This can, for example, be

done readily by interconnecting spring support members in scissorsfashion.

DRAWINGS These and other features and advantages of the presentinvention will be appreciated as the same becomes better understood byreference to the following detailed desciption of presently preferredembodiments when considered in connection with the accompanying drawingswherein:

FIG. 1 is a view of a pair of bifold doors indicating the location ofapplication of hinges constructed according to principles of thisinvention; I

FIG. 2 is a perspective view of a spring hinge constructed according toprinciples of this invention with bifold doors in their closed position;

FIG. 3 is an end view of the hinge of FIG. 2 in its position when thedoors are open;

FIG. 4 is a side view of the hinge from the inside of the doors;

FIG. 5 is a horizontal cross section through the stile I and panel of adoor illustrating in end view one hinge FIG. 9 is an inside view ofone-half of the power pack of FIG. 8;

FIG. 10 is an outside view looking out towards-onehalf of the power packof FIG. 8;

FIG. 1 1 is a detailed cross section of an integral hinge or pivotbetween two halves of the plastic power pack of FIG. 8;

FIG. 12 is a fragmentary side detail of a hinge leaf engaging portion ofthe plastic power pack of FIG. 8;

FIG. 13 is a fragmentary cross section indicating the engagement of theplastic power pack with an aperture through the hinge leaf;-

FIG. 14 illustrates the two moieties of another sheet metal embodimentof power pack useful in a spring hinge for bifold doors;

FIG. 15 illustrates in perspective a spring for the hinge; 1

FIG. 16 is a fragmentary detail of another hinge leaf engaging portionfor a plastic power pack;

FIG. 17 is a fragmentary cross section indicating engagement of theportion of FIG. 16 with an aperture through a hinge leaf; and FIG. 18 isan end view of another embodiment of spring hinge.

DESCRIPTION FIG. 1 illustrates rather generally the location of hingesfor bifold doors. The doors as seen in FIG. 1 are viewed as if one werestanding inside a closet lookiing towards the doors in a nearly closedposition. Such doors 20 and 21 are formed of two panels. The first door20 has pivots 22 at the top and bottom to flt in brackets (not shown) ina door frame adjacent a jamb for mounting the pair of doors. The otherdoor has guides 23 at the top and bottom for riding in a track (notshown) in the door frame. Spring hinges 24 interconnect the two doors 20and 21 at the top and bottom corners. Generally speaking, hereinafterdescription of the hinges will consider that the hinge is mounted at thetop of a pair of doors and top and bottom may be used in that context indescribing various aspects of the structure. It will be apparent, ofcourse, that a substantially identical structure is employed at thebottom of the door. If desired one or more center hinges (not shown) canbe mounted between the end hinges 24 for increased stiffness.

FIG. 2 illustrates in perspective a spring hinge constructed accordingto principles of this invention mounted at the top of a pair of doorswhich are illustrated in their closed position. FIG. 3 is a top view ofthe spring hinge, deleting the doors, with the hinge in the position itwould have with the doors open.

FIG. 4 is a side view of the hinge from the inside of the doors lookingout, with the hinge in a position it would have with the doors closed.Although it may seem contrary to the apparent structure of the hingeitself, reference will be made hereinafter to the hinge in its closedposition representing that condition when doors attached thereto areclosed, that is, with their panels lying in substantially the sameplane.

The doors as seen in FIG. 2 each comprise a flat panel 26 such asplywood, composition board or the like about 3/ l 6 inch thick. Alongthe edge of each door is a stile 27, each of which is roll formed fromflat sheet and has an identical cross section (the two stiles are, ofcourse, reversed relative to each other so as to be symmetrical aboutthe plane between the door edges). Rails 28- are fitted along the topedge of each door panel 26. Similar stiles and rails are employed on theother edges of the panels to complete the door.

As best seen in FIG. which comprises a horizontal cross section lookingupwardly one-half of the hinge, the stile 27 has a front wall 29 inengagement with the front face 31 of the panel 26. A hollow raisedflange 32 is provided along the length of the stile. A jamb edge or sidewall 33 is adjacent the edge of the panel and is opposed to a similarside wall (not shown in FIG. 5) on the adjacent stile on the other door.Typically, the side wall 33 is at an angle of less than from the frontwall 29 when the stile is used on a 3/16 inch panel. This permits thespringiness of the stile to acommodate a A inch panel, if desired andthe stile wall -33 is at about 90 from the panel in that case.

A back wall 34 is approximately parallel to the front wall 31 and isspaced a substantial distance away from the rear face 36 of the panel inorder to provide stiffness. Extending between the back wall 34 and therear face 36 of the panel is an inner leg 37. At the inner end of theinner leg there is an inwardly directed foot 38 that engages the rearface 36 of the panel. A slot 39 is provided through the inner leg 37 asbest seen in FIG. 2.

Thus, it will be seen that the stile has a generally G- shaped crosssection (illustrated inverted in FIG. 5) with the top of the Gcorresponding to the front wall 29 and the bottom of the G correspondingto the back wall 34. The panel enters the mouth of the G between thecrossbar (foot 38) and the top. The springiness of the sheet metalforming the stile accommodates some variation in thickness of doorpanel.

The rail 28 which is best seen in the vertical cross section of FIG. 6and in FIG. 2, is essentially an inverted U-shaped member fitted overthe top edge of the panel and sufficiently springy to frictionallyengage it. A face flange 41 within the hollow rail engages the frontface 31 of the panel. Space is left between the fact 40 of the rail andthe face flange 41 to accommodate a portion of the hinge describedhereinafter and also to provide good abutment at the end of the railagainst the side of the flange 32 on the stile. This prevents the end ofthe rail from slipping between the panel and stile. It is convenientalso to provide a turned in rear flange 42 on the rail which provides arounded portion so that the door panel can easily be inserted duringassembly and which also contributes to the springiness of the rail. Thetop 43 of the rail normally has a slight clearance beyond the edge ofthe door panel. A pair of slots 44 extends through the top of the railadjacent the face flange 41.

Referring again to FIG. 2 and incidentally FIGS. 3 to 6, the hingebetween the two doors is made of two hinge leaves 46 that are anallochiral pair except for one minor feature. Each hinge leaf has anextending ear 47 and a hinge pin 48 preferably in the form of a shortloose rivet extends through the two ears 47 to define the pivot axis ofthe hinge. One of the ears 47 is offset from the top of the hinge leafby an amount equal to the thickness of the metal used to form the hingeleaf so that the two ears can fit together for forming a pivot.Otherwise the two hinge leaves are similar in shape.

Since doors formed of thin panels with peripheral stiles and rails arequite light weight, the short hinge pin formed by the rivet 48 when ahinge is used at both the top and bottom of the door has been foundsufficient. Typically, the entire hinge leaf is blanked and bent fromsheet steel and bearing loads on the pivots are not excessive.

Each hinge leaf is essentially L-shaped with a top arm 49 extending overthe rail 28 and a downwardly extending leg 51 (FIGS. 4 to 6) extendinginside the stile 27.

The laterally extending arm 49 has a top face 52 that flts over the top43 of the rail. Nearer the front of the door a pair of spaced aparttangs 53 extend downwardly through the slots 44 in the top of the rail.As

best seen in FIG. 6 these tangs bear against the face flange-41 of therail which is in engagement with the front face 31 of the panel. Thehinge leaf arm also has a flange 54 extending down from the top 52 onthe back side of the rail, that is, nearer the rear face 36 of thepanel. The flange 54 bears against the corner 56 between the top andback of the rail. The hinge leaf thus firmly grips the rail and hastangs 53 in effective engagement with the front face of the door panelso that the hinge leaf is securely held in alignment with the font ofthe panel. The rather widely spaced apart tangs 53 and the elongatedflange 54 on the arm of the hinge leaf assure accuratealignment of therails and therefore 1 also the door panels. It will be apparent that asingle transfer through the finger 62 to the rest of the hinge. Torelease the hinge leaf from the stile in the rare case where it isdesired to remove'the hinge, one need only strike the barb with a punchto bend the finger 62.

. stiles and pressing down until the tangs 53 enter the front face ofthe doors. The two stops are in tight ennot readily be pushed past theiraligned, closed 'positron.

An additional tang 57 also extends downwardly from the top of the hingeleaf into the interior of the front flange 32 on the stile. An edge ofthe tang 57 engages the frontface 31 of the door panel. If desired, thestile may include an additional folded portion on the front flange thatlies adjacent the front face of the panel and essentially makes thefront flange 32 a box section. When that is done the tang 57 has an edgeengaging this additional flange. This third tang 57 serves to furtherassure alignment of the hinge leaf with the door panel. In addition, ithelps secure the stile in fixed relation to the end of the rail asdetermined by the spacing of the slots 44 from the end of the rail. In astile where the front flange 32 is deleted, the third tang 57 may alsobe deleted.

As best seen in the horizontal cross section of FIG. 5, the downwardlyextending leg 51 of the hinge leaf has an approximately, U-shaped crosssection over much of its length. The bight 58 of the U is adjacent theside wall 33 of the stile. The bight of the U-shaped portion of the legextends upwardly and connects the leg to the arm of the hinge leaf at afold 60 (FIG. 2). A plane leg 59 of the U-shaped cross section isrelatively nearer the door panel and approximately parallel thereto. Thespan of this plane leg 59 is sufficient to engage the inner leg 37 ofthe stile. The other leg of the U'shaped cross section has a slot 61(FIG. 4) extending upwardly from its lower end. This slot defines afinger 62 extending downwardly along the leg. A barb 63 on the end ofthe finger 62 snaps into the slot 39 through the inner leg 37 of thestile. The finger and barb cooperate with the stile in a manner somewhatsimilar to related elements in US. Pat. No. 3,450,426. The barb alsopicks up loads due to the weight of the door for slots 44 and the tang57 enters the forward flange 32. As the hinge is pressed further downthe barb snaps into the slot 39 and installation is complete.

I-Iinge leaves as described to this point thus serve to hold the railand stile together, serving as corner connectors for the doors. Thehinge leaves are pivotally interconnected and thereby operate insubstantially the same manner as conventional hinges. In addition, ashereinafter described, spring loading is applied to the hinge leaves foropening or closing the doors and retaining them in their respectiveextreme positions.

A window or aperture 64 is provided in the top face 52 of each of thehinge leaves. This window has a generally L-shape with a projection orbearing tooth 66 extending into the window. The bearing tooth pointsaway from the hinge pivot 48. The included angle of the bearing tooth 66in this embodiment is about Referring to FIG. 2 it will be noted that aline between the points of the bearing teeth 66 on the two hinge leaveslies to one side of the axis ofthe pivot 48 between the two hingeleaves. FIG. 2 illustrates the hinge in its closed position. Referringto FIG. 3 where the hinge is illustrated in its open position, it willbe noted that a line between the bearing teeth 66 on the two hingeleaves now lies on the opposite side of the pivot axis from itsposition, when the hinge was closed. Each of the bearing teeth movesalong a circular are about the axis of the pivot 48 as the hinge ismoved between its closed and open positions. The two bearing teeth arerelatively closer together in the closed position, and in the openposition, than they are at the intermediate over-center" point where theline therebetween intersects the pivot axis.

If a force is applied in a direction urging the bearing teeth towardseach other, (as, for example, by a tension spring therebetween) thehinge in its closed position will tend to stay closed. Any motiontending to open the hinge must overcome this urging force (and stretchthe imaginary tension spring). Similarly when the hinge is in its closedposition, any movement tending to open the hinge spreads the bearingteeth further apart and must overcome the urging force. At theintermediate point where the line between the bearing teeth intersectsthe pivot axis the imaginary spring is stretched to its maximum extentand on either side of this intermediate point this spring would urge thehinge towards either its open or closed position.

Such an over-center action tending to open or close the hinge dependingon whether it is more nearly open or nearly closed, respectively, couldbe obtained by simply providing posts above the top of the hinge atpoints corresponding to the location of the bearing teeth. A tensionspring therebetween would move over center when crossing the pivot axisand provide the opening and closing biasing forces for operating thehinge. Such an arrangement is, however, undesirable since the springwould extend a significant distance beyond the top of the hinge andmight interfere with guide tracks or beocme tangled in carpeting. Othermeans are therefore desirable for applying a force between the bearingteeth without extending any substantial distance above the hinge. Aspring power pack is provided for biasing the hinge.

It might be noted that a complete over-center action is not needed. Themore important function is to assure that the doors are completelyclosed and aligned with the stops 55 in engagement. It is not assignificant to force the doors to a completely open position. It istherefore feasible to have the spring force applied on one side of thepivot axis when the doors are closed and substantially across the pivotaxis when the doors are open. The open position may be less stable, butthis is not a substantial problem since the closing spring force exertedat the center position is rather small. Thus it is broadly feasible tohave a spring hinge wherein the pivot is on one side of the spring forcewhen the doors are closed and not on the same side when the doors areopen. That is, when the doors are open the spring force line may be onor beyond the center position defined by the hinge pivot axis. When oncenter there is no force tending to either open or close the doors. Whenbeyond center the doors are biased open. It is preferable to bias thedoors open as well as closed.

In the embodiment illustrated in FIGS. 2 to 4, the power pack comprisesa first rigid spring support member 67 and a second spring supportmember 68 in many respects similar to the first. Each of the springsupport members 67, 68, is generally U-shaped with a crooked or curvedspring arm 69 and a crooked or curved bearing arm 71 aproximatelyparallel to the spring arm. These two arms are interconnected by a flatbight portion 72. The spring support members are simply blanked and bentfrom sheet steel. The tip of the bearing arm 71 is bent towards thespring arm to define a bearing surface 73 at approximately a right angleto the principal extent of the bearing arm. The bearing surfaces arepreferably substantially normal to a line therebetween. A second bendbeyond the bearing surface forms a hook 74 approximately parallel withthe principal extent of the bearing arm. As best seen in FIGS. 2 and 3the power pack is assembled to the hinge leaves with the end of thebearing arm extending through the window 64 so that the hook 74 isbeneath the bearing tooth 66 and the bearing surface 73 is in engagementwith the tip of the bearing tooth.

'A coil spring 76 (illustrated only in FIG. 2 and deleted from FIGS. 3and 4) is hooked into a notch 77 at the end of each of the respectivespring arms 69. This places the spring parallel to the line between thebearing surfaces 73. When the two spring support members 67'and 68 areinterconnected by a pivot transverse to the spring axis, the spring willurge the bearing surfaces towards each other. Such a pivot can beprovided by a pin extending parallel to the bight portions 72, however,this tends to present minor manufacturing and economic problems that arepreferably avoided.

A pivot between the two bearing support members need only move through afew degrees of arc during operation of the power pack in the bifold doorhinge. A

female quasi-cylindrical socket 78 is formed along one edge of the bightportion 72 on the first spring support member 67. A male knife edge isformed on the corresponding edge of the bight portion 72 of the secondspring support member 68. When assembled the knife edge 79 rests in thesocket 78 and is free to tilt therein about an axis transverse to thearms 69 and 71 on the spring support members. A short tang 81 extendsfrom each of the arms of the first spring support member 67 between thecorresponding arms of the second spring support member 68 for inhibitinglateral movement of the knife edge along the quasi-cylindrical femalesurface, thereby holding the spring support members to gether.

It will be apparent that an extremely blunt knife edge is actuallyinvolved in this embodiment corresponding to the thickness of the sheetmetal used for forming the spring support members. Such a very im'precise fit at the quasi-cylindrical socket and knife edge pivot isquite satisfactory since operation of the power pack is ratherinsensitive to location of the pivot, loads on the pivot are rathersmall, and neither wear nor friction of the pivot is any problem.

The power pack is readily assembled merely by hooking the knife edge 79into the socket 78 and pivoting to fit the tangs 81 between the arms ofthe second support member. The spring 76 is then snapped in place in thenotches 77. The step 82 adjacent the tangs 81 limits the extent the armscan pivot towards each other under the urging of the spring. Thispreassembled power pack is then assembled to the hinge when the hinge isin its closed position as illustrated in FIG. 2. The windows 64 throughthe top of the hinge leaves have a sufficient extent in a directionalong the rail arm 49 to provide clearance for the hook 74. The powerpack is inserted by pivoting the arms away from each other (therebystretching the spring) and dropping the hooks through the correspondingwindows. When the arms are released the urging of the spring retains thebearing surfaces 73 in engagement with the bearing teeth 66 and inhibitswithdrawal of the power pack. The hooks 74 engaging the underside of thehinge leaf also inhibit rotation of the power pack about an axisextending between the bearing teeth. Engagement of the bearing arms 71with the top 52 of the hinge leaf inhibits rotation about the same axisin the opposite direction.

Thus it will be seen that with the power pack installed on the hinge asabove described, the force of the spring is effectively transferredthrough the spring support members and is applied in a direction betweenthe two bearing surfaces 73. The magnitude of the force exerted by thebearing forces on the bearing tooth is readily selected by the magnitudeof the spring force and the relative lengths-of the lever arms formed bythe spring arms 69 and bearing arms 71, respectively.

It might be noted that functionally the power pack is analogous to ascissors linkage. A closing force exerted on the spring arms actsthrough the pivot to cause the bearing arms to exert a closing force. Ifdesired, instead of employing U-shaped spring support members pivotallyinterconnected along an axis extending along the bight of the U, one canuse pivotally interconnected straight spring support members in directscissors fashion. One difficulty raised by such an arrangement, however,is that the power pack extends a substantially greater distance awayfrom the hinge pivot axis and may, for example, interfere with objectsin a 9 closet when the doors are closed. In the illustrated arrangementthe power pack intrudes into a-closet a mini-' mum distance and thespring is removed to a position below the top of the hinge so as not tointerfere with the tracks at the ends of the doors. a

The power pack applies the spring force in a direction along the linebetween the bearing teeth 66 thereby urging the hinge towards its closedpositions when it is more nearly closed and towards its open positionwhen it is more nearly open. The bearing arms of the spring supportmembers can be connected to the hinge leaves by ordinary pivot pinsrather than the illustrated arrangement, however, this raises minormanufacturing or economic problems which are preferably avoided. Thenumber of parts required to make a complete spring hinge is alsoincreased with a concomitant increase in cost. Each of the hinge leavesmust pivot through an angle of only about 90 in passing between the openand closed positions. It therefore becomes feasible to employ thepointed tip of the tooth 66 and the flat bearing surface 73 as a knifeedge and plane pivot. Such a knife edge is not quite a point contactsince the tooth has a finite bearing surface on the plane. With steelparts having the relatively small bearing loads applied by the powerpack, the contact area is very small and the motion is effectively oneof tilting,

thereby causing very little friction or wear. The included angle of thetooth should be no more than 90 to keep the bearing surface fromengaging the side of the tooth.

It is apparent that the relative positions of the bearing tooth andplane surface can be reversed. That is, the bearing tooth can be on thepower pack and the bearing surface can be in the window on the top ofthe hinge leaf. The illustrated arrangement is preferred because ofmanufacturing considerations. The important consideration is that therebe at least 90 of clearance be-,

I tween the bearing tooth and the bearing surface. That is, the totalincluded angle of both the bearing tooth and bearing surface be no morethan about 270. This is needed since collectively the hinge halves mustpivot through 180 and the connection between the power pack and eachhinge leaf must swing through 90. Many intermediate arrangements betweenthe knife edge and plane with an included angle of no more than 270 willbe'apparent toone skilled in the art. Even arrangements with an obtuseincluded angle in both the bearing tooth and the bearing surface may besuitable so long as some means is provided for preventing the points ofthe two obtuse angles from slipping laterally from each other, thus, forexample, a minor indentation may be provided at the apex of one of theobtuse angles.

I Some small additional angular clearance is preferable between thebearing tooth and surface so that the motion of the hinge is limited byother builtin stops. The hinge extends to alignment in its closedposition as lim- I since they tend to bind when one attempts to closethem. Instead the doors diverge at about 10 to give the second door somelead so that it will slide along the track when the first door is pushedin a direction parallel to the door frame. The engagement of the railswith the power pack may be suitable means for maintaining suchdivergence, but it is preferred that an auxilliary stop be added afterthe doors are hung. This permits doors with installed hinges to lieparallel for packing and shipping.

The power pack hereinabove described and illustrated in FIGS. 2 to 4, isconveniently blanked and bent from cold rolled sheet steel. It has alsoproved highly advantageous to form a power pack of injection moldedplastic. When such a power pack is molded of polypropylene, the livinghinge properties inherent in this plastic can be utilized. Othersuitable plasticsinclude some varieties of nylon and acetal resins.Fibers in this plastic are readily oriented by stressing (possibly whileslightly warm) to provide a flexible hinge that can be cycled a greatnumber of times without failure.

FIG. 7 illustrates in perspective the general arrangement of such amolded plastic power pack. As illustrated in this embodiment the powerpack is formed of two rigid spring support members 86 which are anallochiral pair. Each of the spring support members has a spring arm 87on which a spring 88 is mounted as hereinabove described.

A bearing arm 89 is parallel to the spring arm 87 on each half of thepower pack. The spring arm in such an embodiment may be approximatelysemi-circular for enhanced rigidity with a relatively thin section. Thebearing arms are preferably made relatively thin so as to have minimumheight above the top of the hinge leaves when the power pack isinstalled.

At the end of each of the bearing arms 89 there is an offset hook 91 forfitting through the window in a hinge leaf and holding the power packagainst removal in the manner hereinabove described. A bearing face 92is on the end of the bearing arm adjacent the hook 91. A shallow groove93 is provided in the center of the bearing face to provide a region ofcontact with the bearing toothon a hinge leaf. The bearing tooth (notshown) on a hinge for use with a plastic power pack is preferablyprovided with a radius as hereinafter described in greater detailbecause the bearing strength of the plastic is not as great as that ofsteel and it is desirable to have a larger area of contact betweenthe'tooth and bearing surface when one or both of the parts is made ofplastic than when both are made of steel. A point or knife edge contactby steel on the plastic would introduce an unacceptably high localizedbearing load. When the bearing tooth with a radius on the end thereof isused it may not be necessary to provide a preformed groove 93 since thetooth will make its own groove in a few cycles of operation. Thereafterwear of the polypropylene as the hinge is used is only minimal.

The two rigid bearing support members 86 are interconnected at theirbight portions by a thin web 94 of polypropylene integral with thespring support members. Such a web between the two halves will flex avery large number of cycles and thereby provides a pivotalinterconnection between the two spring support members. When the plasticpower pack is injection molded, the two halves are fonned in anunfolded" position, that is, with the web 94 extending substantiallystraight between the two halves lying side by side with the bearingsurfaces 92 on the two halves being in pproximately the same plane.Thereafter the two halves are folded towards each other to a positionsuch as that shown in FIG. 7 for receiving the spring 88. This bends theweb 94 as shown to provide a pivotal interconnection between the bearingsupport members.

FIGS. 8, 9 and 10 illustrate in bottom, inside, and outside viewsrespectively another embodiment of molded plastic power pack. In each ofthese figures one-half of the power pack is illustrated and it will beunderstood that an allochiral half is omitted. In the three views ofFIGS. 8 to 10 the omitted half of the power pack would be lying adjacentthe illustrated half in the position occupied during molding of theplastic part before the integral hinge is bent, that is, in top view thepower pack would look something like one-half of a figure 8 rather thanthe approximately circular position illustrated in FIG. 7. FIGS. 11 to13 are fragmentary views showing details of the plastic power pack.

The top portion of the power pack is approximately a semicircularbearing arm 96. This bearing arm is bowed upwardly at its middle portionand a shallow relief cavity 97 is provided on the underside forclearance over the pivotal interconnection between a pair of hingeleaves of the same general type hereinabove illustrated in FIG. 2. Thelower part of the spring support member comprises a spring arm 98 with anotch 99 towards the outside thereof for receiving a tension spring (notshown). Interconnecting the bearing arm 96 and the spring arm 98 is abight portion 101. To provide sufficient strength in the bight portionit is formed with a generally S-shaped or Z-shaped wall 102 best seen inFIG. 8, extending between the bearing arm and the spring arm.Reinforcing webs 103 extend across the crooks of the S-shaped wall anddefine recessed pockets 104 facing towards both the inside and outsideof the power pack half. These pockets are provided rather than merelymaking the bight portion of one mass of plastic in order to keep thesection thickness of the plastic relatively uniform throughout themolded part. Stiffness can also be enhanced with a steel insert in thebight.

An integral web 106 of polypropylene extends between the bight portionof the illustrated half of the plastic power pack and that half deletedfrom FIGS. 8 to 10. The web 106 is initially molded approximately flaton its inside face and concave on its outside face as best seen in thelower right portion of FIG. 8. When the hinge is folded as illustratedin FIG. 11 to bring the two spring support members into face to faceproximity the web 106 is bent so that the initially flat face is rathersharply concave towards the inside of the power pack and the originallyconcave portion of the web on the outside is now convex.

At the outer end of the bearing arm 96 there is a hok 107 shown fromthree directions in FIGS. 8 to 10, andd in the enlarged side view inFIG. 12. In addition, a cross section through the base of the hook isillustrated in FIG. 13 along with a window 108 through the top of ahinge leaf not otherwise illustrated but in most respects similar tothat hereinabove described and illustrated in FIGS. 2 to 4.

The hook 107 has an approximately cylindrical portion 109, except for acut-away side to provide sufficient clearance for the hook to passthrough the window 108. Four tapered ribs 111 extend beyond thecylindrical portion for reinforcement and provide a taper thecylindrical part 109 and the bearing arm 96 exposes a surface 112.

Referring to FIG. 13 a bearing tooth 113 extends into the window 108 ina manner analogous to the bearing tooth 66 seen in FIGS. 2 and 3. Inthis embodiment the bearing tooth has a rounded end portion 114extending through an angle of about 270 around the end of the bearingtooth. A mating groove 116 is formed in the surface 112. As mentionedhereinabove the bearing groove 116 may be provided initially in themolding process or it may occur after a few cycles of operation of thepower pack in conjunction with a hinge. The mating of the rounded end114 on the bearing tooth and the bearing surface 116 assures asufficient contact area therebetween for sustaining the loads betweenthe plastic power pack and the hinge leaf. There will be some slidingbetween the rounded end of the bearing tooth and the plastic bearingsurface but since the loads are relatively small very little wear occursand such a hinge and power pack may be operated through many hundreds ofthousands of cycles.

FIG. 14 illustrates an additional embodiment of spring power pack whichmay be blanked and bent from sheet steel. As illustrated in thisembodiment the two spring support members 120 are essentially similar tothose hereinabove described and illustrated in FIGS. 2 to 4. Each springsupport member has a bearing tooth on a hinge leaf. A spring arm 123 isconnected to each bearing arm by a bight portion 124. The bight portionon one of the spring support members has an inwardly folded flange 125having slots 126 at each end. The bight portion on the other springsupport member has an inwardly directed flange 127 that when assembledis approximately opposite the flange 125 on the first spring supportmember.

A hook 128 extends from the second flange 127 a short distance from theend thereof. A tang 129 extends from the flange at the opposite endthereof. At some point between the ends, preferably nearer the tang 129,and spaced from the end of the second flange there is a raised post 131.More than one such post may be provided, if desired. To assemble the twospring support members the hook 128 is inserted through one of the slots126 and the spring support member is slid downwardly so that the tang 12 9 fits through the other slot. The post 131 limits the extent that thetwo spring support members can approach each other since it bearsagainst the flange 125. When this power pack is so assembled with aspring between the spring arms 123 and the hooks through the windows ofhinge leaves, the flange 125 can rock on the knife edge post 131 andhook 128 and provide a pivotal interconnection between the two springsupport members. The spring force tending to pull the spring supportmembers together is counteracted by the post 131. The separating forceacting on the hooks 122 at the upper end is counteracted by the hook128. these two force couples keep the spring support members stable inall operating positions.

FIG. 15 illustrates in perspective a U-spring which can be substitutedfor the power pack in engagement with hinge leaves. The U-spring has apair of opposed bearing arms 133, each of which terminates in a hook134. The hooks 134 are stepped down from the plane of the bearing arms133 to define bearing surfaces 136. The hooks and bearing surfaces fitthrough windows in a hinge leaf and cooperate with the bearing tooth inillustrated in'FIGS. 2 to 4. Interconnecting the two bearing arms 133'and folded from the same sheet of steel is an elastic bight portion 137.

The bightportion is itself substantially U-shaped and the upper part ofthe central bight is relatively narrow to provide clearance for therails (not shown) when the power spring is assembled on a hinge. Thelower part of the bight portion is relatively enlarged for optimumstress distribution.

When the U-spring is engaged with a pair of hinge leaves, movement ofthe hinge leaves flexes the elastic bight portion 137 and the elasticitythereof spring biases the hinge in substantially the same manner as thepower pack.

According to another arrangement not illustrated herein, a torsionspring having a single torsion loop with its axis parallel to the hingepivot axis and end prongs fitting through windows in the top of thehinge leaf may provide the over-center operation of the hinge.Similarly, as illustrated ,in FIG. 18 a C-shaped spring 151 similar'to aretaining ring may be riveted through apertures in the mp of the hingeleaf by rivets 152. The other parts of the spring hinge are numbered thesame as in FIGS. 1 to 6. Many other spring arrangements will be apparentfor alternatively biasing the hinge leaves towards their closed oropened positions.

FIGS. 16 and 17 illustrate another embodiment of hook for a moldedplastic power pack and a corresponding hinge. leaf window suitable forpractice of this invention. As illustrated in this embodiment there is ashort cylindrical post 141 extending downwardly from one bearing arm 142of a molded plastic spring power pack. A cylindrical hook 143 is beyondthe cylindrical post 141 and eccentric therewith.

The hinge leaf 144 has a keyhole shaped window 146 in substantially thesame position as a corresponding window in the embodiment illustrated inthe embodiment illustrated in FIGS. 2 to 4-. At one side of the windowrelatively nearer the hinge pivot axis (not shown) the window hasaconcave cylindrical surface 147 having the .same radius as thecylindrical post 141. Typically the center portion of this cylindricalsurface 147 is between the hinge pivot axis and the center of the post.The cylindrical bearing surface on the hinge leaf engaging thecylindrical post provides a pivotal interconnection between the powerpack and a hinge much in the manner hereinabove described. The plasticpost rotates within the window in the'hinge leaf during operation, butsince the bearing area is quite large and the -a hinge pivotinterconnecting the first and second hingeleaves forpivoting between anopen position and a closed position; I

a first spring support member having a general U- shape with a first endin pivotable engagement with the first hinge leaf;

a second spring support member having a general U- shape with a firstend in pivotable engagement with the second hinge leaf;

said hinge pivot being on one side of a line between v the loci ofpivotable engagement of the respective spring support members with thehinge leaves in the closed position and not on the same side of the linein the open position; means for pivotably interconnecting the first andsecond spring support members in scissors fashion comprising a pivothaving a pivot axis along the bight of the U, said pivot axis beingsubstantially parallel to the pivot axis of the hinge pivot; and

spring means on the same side of the pivot axis of the spring supportmembers as is the pivot axis of the hinge pivot interconnecting thesecond ends of the respective spring support members for urging thesecond ends towards each other.

-.2. A spring hinge as defined in claim 1 wherein the means forpivotably interconnecting the first and second spring supportmemberscomprises:

- a quasi-cylindrical socket on the bight of the first spring supportmember, the interior of the socket facing the hinge pivot axis; and

a knife edge on the bight of the second spring support member engagingthe interior of the socket.

3. A spring hinge as defined in claim 1 wherein the hinge leaves eachcomprise a window through the top of each hinge leaf and a bearing toothextending into the window, and wherein each spring support membercomprises a hook extending down through a respective one of said windowsand a bearing surface in engagement with the respective bearing toothfor pivoting about an axis parallel to the pivot axis of the hingepivot; and each spring support member has a bearing arm extending over arespective hinge leaf and each hook comprises a stud-like projectionbelow the bearsaid hinge pivot being on one side of a line between theloci of pivotable engagement of the respective spring support memberswith the hinge leaves in the closed position and not on the same side ofthe line in the open position;

means for pivotably interconnecting the first and sec-- ond springsupport members in scissors fashion; and

- spring means interconnecting the second ends of the respective springsupport members for urging the second ends towards each other; andwherein the hinge leaves each comprise a window through the hinge leafand a bearing tooth extending into the window, and

each spring support member comprises a hook extending through arespective one of said windows and a bearing surface in engagement withthe respective bearing tooth.

5. A spring hinge as defined in claim 4 wherein each spring supportmember has a bearing arm extending over a respective hinge leaf and eachbearing surface comprises an end extension of the bearing arm goingthrough the respective window and each hook comprises an extensionbeyond the bearing surface and fitting under the bearing tooth.

6. A spring hinge comprising:

a first hinge leaf;

a second hinge leaf;

a hinge pivot interconnecting the first and second hinge leaves forpivoting between an open position and a closed position;

a window through the top of each hinge leaf, the pivot axis of the hingepivot being on one side of a line between the windows with the hingeleaves in the closed position and not on the same side of the line withthe hinge leaves in the open position;

pivot means extending down through each window, the pivot axes of thepivot means being parallel to the pivot axis of the hinge pivot;

spring means for exerting a biasing force;

means for transmitting the biasing force from the spring to the pivotmeans for exertion on the hinge leaves in a direction primarily betweenthe pivot means, said spring means being at least partly below thewindows; and

means on the portion extending through each window for inhibitingremoval of the pivot means from the respective window.

7. A spring hinge as defined in claim 6 wherein the means fortransmitting and the spring means are an integral U-shaped memberwherein the center portion is elastically deflectable and the arms ofthe U are substantially rigid, the center portion being approximatelynormal to the plane of the U as defined by the arms thereof.

8. A spring hinge as defined in claim 7 wherein the pivot meanscomprises a hook on the end of each arm of the U-shaped member extendingthrough the window.

9. A spring hinge as defined in claim 7 wherein the center portion ofthe U-shaped member has a U-shape extending a substantial distancebeyond the plane defined by the arms, and wherein the upper part of theU- shaped center portion is relatively narrower than the lower partthereof.

10. A spring hinge as defined in claim 6 wherein the hinge pivot is onthe other side of the line between the loci of pivotable engagement withthe hinge is in its open position.

11. A spring hinge as defined in claim 6 wherein the means fortransmitting comprises:

a pair of rigid U-shaped spring support members each comprising abearing arm connected to the pivot means, a spring arm connected to thespring means, and a bight portion interconnecting the bearing arm andthe spring arm; and

means interconnecting the spring support members along the bightportions thereof for pivoting about an axis parallel to the hinge pivotaxis.

12. A spring hinge as defined in claim 11 wherein the spring supportmembers are molded plastic and the means for pivoting comprises aflexible web of plastic integral with both spring support members andextending therebetween.

13. A spring hinge as defined in claim 6 wherein the hinge leaves eachcomprise a window through the hinge leaf having a concave cylindricalbearing face and wherein the means for transmitting the biasing forcecomprises a hook extending through a respective one of said windows anda cylindrical bearing surface in engagement with the respective bearingface.

14. A spring hinge as defined in claim 6 wherein the pivot means and themeans for inhibiting removal comprise; a bearing surface extendingthrough the window and a hook beneath a portion of the hinge leafadjacent the window.

15. A spring hinge as defined in claim 14 wherein each hinge leafcomprises a cylindrical bearing surface in the window and the pivotmeans comprises a cylindrical post engaging the cylindrical bearingsurface in the window.

16. A spring hinge comprising:

a first hinge leaf;

a second hinge leaf;

a hinge pivot interconnecting the first and second hinge leaves forpivoting between an open position and a closed position;

a window through the top of each hinge leaf, the pivot axis of the hingepivot being on one side of a line between the windows with the hingeleaves in the closed position and not on the same side of the line withthe hinge leaves in the open position;

pivot means extending down through each window, the pivot axes of thepivot means being parallel to the pivot axis of the hinge pivot;

spring means for exerting a biasing force;

means for transmitting the biasing force from the spring to the pivotmeans for exertion on the hinge leaves in a direction primarily betweenthe pivot means, said spring means being at least partly below thewindow; said means for transmitting comprising:

a pair of rigid U-shaped spring support members each comprising abearing arm connected to the pivot means, a spring arm connected to thespring means, and a bight portion interconnecting the bearing arm andthe spring arm, and

means interconnecting the spring support members along the bightportions thereof for pivoting about an axis parallel to the hinge pivotaxis; and

means for inhibiting removal of the pivot means from the respectivewindow; and wherein one of the spring support members comprises a femalesocket and the other spring support member comprises a male memberengaging the female socket for forming the means for pivoting. 17. Aspring hinge as defined in claim 16 wherein the female socket comprisesa concave cylinder facing the hinge pivot axis and the male membercomprises a knife edge fitted into the cylinder.

18. A spring hinge comprising:

a first hinge leaf;

a second hinge leaf;

a hinge pivot interconnecting the first and second hinge leaves forpivoting between an open position and a closed position;

a window through the top of each hinge leaf, the

pivot axis of the hinge pivot being on one side of a line between thewindows with the hinge leaves in the closed position and not on the sameside of the line with the hinge leaves in the open position;

' pivot means extending down through each window, the pivot axes of thepivot means being parallel to the pivot axis of the hinge pivot; I

spring means for exerting a biasing force;

means for transmitting the biasing force from the spring to the pivotmeans for exertion on the hinge leaves in a direction primarily betweenthe pivot means, said spring means being at least partly below thewindow;

means for inhibiting removal of the pivot means from the respectivewindow;

' the pivot means and the means for inhibiting removal comprising abearing surface extending through the windowand a hook beneath a portionof the hinge leaf adjacent the window; and wherein each hinge leafcomprises-a bearing tooth in the window in engagement with the bearingsurface, the total included angle of the bearing tooth and bearingsurface being less than about 270.

19. A spring hinge as defined in claim 6 wherein the means fortransmitting and the spring means are an integral C-shaped spring; andwherein the pivot means comprises a rivet through'each window.

20, A spring hinge for a pair of bifold doors each having a door panel,a stile along each of the side edges of the panel, and a rail along eachend of the panel comprising;

. first and second hinge leaves, each hinge leaf comprising a leg forengaging a stile and an arm for fitting over the top of a rail andengaging therewith for connecting the rail and stile together;

a hinge pivot interconnecting the hinge leaves for I pivoting between anopen position with rails in alignment anda closed position with railsside by side;

spring means below the top of the rail for exerting a biasing force; and

a pair of rigid U-shaped spring support members each comprising abearing arm pivotally connected to a respective hinge leaf, a spring armconnected to the spring means, a bight portion interconnecting thebearing arm and the spring arm, and means interconnecting the springsupport members along the bight portion thereof for pivoting about anaxis parallel to the hinge pivot axis for biasing the leaves towardseachother along a line lying on one side of the hinge pivot axis when inthe closed position and on the other side when in the open position.

' 21. A spring hinge as defined in claim 20 wherein the socket on one ofthe spring support members and a male knife edge on the other springsupport member engaging the female quasi-cylindrical socket, said maleknife edge and female cylindrical socket extending parallelto the hingepivot axis.

22. A spring hinge as defined in claim 20 wherein the pivotalinterconnection between the bearing arm and respective hinge leafcomprises a first bearing surface on the hinge leaf adjacent a windowthrough the hinge I means for pivot ng comprises a female cylindricalleaf, a second bearing surface on the bearingarm engaging the firstbearing surface on the hinge leaf, and a hook beneath a portion of thehinge leaf adjacent the window.

23, A spring hinge as defined in claim 22 wherein the first bearingsurface comprises a bearing tooth in engagement with the second bearingsurface and wherein the total included angle of the bearing tooth andbearing surface is less than about 270.

24. A spring hinge comprising a first hinge leaf;

a second hinge leaf;

a hinge pivot interconnecting the first and second hinge leaves forpivoting between a closed position and an open position;

a first bearing tooth on the first hinge leaf;

a second bearing tooth on the second hinge leaf, said hinge pivot beingon one side of a line between the bearing teeth on the two hinge leavesin the closed position and not on the same sideof the line in the openposition;

a first spring support member having a first bearing face in engagementwith the first bearing tooth;

a second spring support member having a second bearing face inengagement with the second bearing tooth;

means for interconnecting said first and second spring support members;

means for retaining the first and second bearing faces in engagementwith the first and second bearing teeth respectively; and

means for urging thefirst bearing face towards the second bearing facein a direction along a line between the two bearing teeth.

25. A spring hinge as defined in claim 24 wherein the hinge pivot is onthe other side of the line between the loci of pivotable engagement whenthe hinge is in its open position. I

26. A spring hinge as defined in claim 25 wherein the first and secondbearing teeth each comprise an opening in the respective hinge leaf anda projection extending into the opening from one side thereof, saidprojection pointing in a direction away from the hinge pivot; and

the bearing faces each comprise a portion of the spring support memberextending through the opening.

27. A spring hinge as defined in claim 26 wherein the means forretaining comprises a tang on the end of each spring support memberbeyond the respective bearing face and extending along one face of theprojection approximately in the direction of the line between thebearing teeth.

28. A spring hinge as defined in claim 27 wherein the first and secondspring support members are opposite arms of a U-shaped member, thecentral portion of the U-shaped member being elastically bendable.

29. A spring hinge as defined in claim 27 wherein:

each spring support member has a generally U-shape with a bearing armhaving the respective bearing face near the end thereof and a springarm;

the means for interconnecting the first and second spring supportmembers comprises a pivot having a pivot axis along the bight of the U;and

the means for urging comprises a tension spring between spring arms.

30. A spring hinge as defined in claim 25 wherein the first and secondspring support members, the means for interconnecting and the means forurging collectively are an intergal U-shaped member having the bearingfaces at the opposite ends thereof and wherein the central portion iselastically bendable.

31. A spring hinge as defined in claim 30 wherein each spring supportmember is on one side of its respective hinge leaf wherein the means forretaining comprises:

a tab on each end of the U-shaped member engageable with the side of therespective bearing tooth opposite from the side the spring supportmember 32. A spring hinge as defined in claim 24 wherein the first andsecond spring support members are each a molded plastic member and themeans for interconnecting the spring support members comprises a web ofplastic integral with both of the spring support members and extendingparallel to the hinge pivot axis.

33. A spring hinge as defined in claim 24 wherein the spring supportmembers are molded plastic and the means for interconnecting comprises aflexible web of plastic integral with both spring support members andextending therebetween.

34. A spring power pack comprising:

a first rigid U-shaped spring support member;

a second U-shaped spring support member, said first and second springsupport members each comprising a bearing arm, a spring arm and a bightportion interconnecting the bearing arm and the spring arm;

means interconnecting the first and second spring support members alongthe bight portions thereof for pivoting about an axis along the bightportion;

means on each of the pair of spring arms for connecting a springtherebetween; and

bearing means on each bearing arm for pivotally engaging a matingbearing surface, said bearing means on the respective spring supportmembers facing each other for exerting a compression force therewith.

35. A spring power pack comprising:

a first rigid U-shaped spring support member;

a second U-shaped spring support member, said first and second springsupport members each comprising a bearing arm, a spring arm and a bightportion interconnecting the bearing arm and the spring arm;

means interconnecting the first and second spring support members alongthe bight portions thereof for pivoting about an axis along the bightportion comprising a female quasi-cylindrical socket on one of thespring support members and a male knife edge on the other spring supportmember engaging the quasicylindrical socket, said male knife edge andfemale quasi-cylindrical socket extending parallel to the bightportions;

means on each of the pair of spring arms for connecting a springtherebetween; and

bearing means on each bearing arm for pivotally engaging a matingbearing surface, said bearing means on the respective spring supportmembers facing each other for exerting a compression force therewith.

36. A spring power pack as defined in claim 35 wherein the bearing meanscomprises a fiat surface extending substantially normal to the bearingarm towards the spring arm and a hook portion extending beyond thebearing portion in a plane parallel to the plane of the bearing arms.

37. A spring power pack ccomprising:

a first rigid U-shaped spring support member;

a second U-shaped spring support member, said first and second springsupport members each comprising a bearing arm, a spring arm and a bightportion interconnecting the bearing arm and the spring arm;

means interconnecting the first and second spring support members alongthe bight portions thereof for pivoting about an axis along the bightportion;

means on each of the pair of spring arms for connecting a springtherebetween; and

bearing means on each bearing arm for pivotally engaging a matingbearing surface comprising a fiat surface extending substantially normalto the bearing arm towards the spring arm and a hook portion extendingbeyond the bearing portion in a plane parallel to the plane of thebearing arms, said bearing means on the respective spring supportmembers facing each other for exerting a compression force therewith.

1. A spring hinge comprising: a first hinge leaf; a second hinge leaf; ahinge pivot interconnecting the first and second hinge leaves forpivoting between an open position and a closed position; a first springsupport member having a general U-shape with a first end in pivotableengagement with the first hinge leaf; a second spring support memberhaving a general U-shape with a first end in pivotable engagement withthe second hinge leaf; said hinge pivot being on one side of a linebetween the loci of pivotable engagement of the respective springsupport members with the hinge leaves in the closed position and not onthe same side of the line in the open position; means for pivotablyinterconnecting the first and second spring support members in scissorsfashion comprising a pivot having a pivot axis along the bight of the U,said pivot axis being substantially parallel to the pivot axis of thehinge pivot; and spring means on the same side of the pivot axis of thespring support members as is the pivot axis of the hinge pivotinterconnecting the second ends of the respective spring support membersfor urging the second ends towards each other.
 2. A spring hinge asdefined in claim 1 wherein the means for pivotaBly interconnecting thefirst and second spring support members comprises: a quasi-cylindricalsocket on the bight of the first spring support member, the interior ofthe socket facing the hinge pivot axis; and a knife edge on the bight ofthe second spring support member engaging the interior of the socket. 3.A spring hinge as defined in claim 1 wherein the hinge leaves eachcomprise a window through the top of each hinge leaf and a bearing toothextending into the window, and wherein each spring support membercomprises a hook extending down through a respective one of said windowsand a bearing surface in engagement with the respective bearing toothfor pivoting about an axis parallel to the pivot axis of the hingepivot; and each spring support member has a bearing arm extending over arespective hinge leaf and each hook comprises a stud-like projectionbelow the bearing arm for inhibiting removal and the bearing surfacecomprises an undercut portion on the projection, and wherein the springmeans is at least partly below the windows.
 4. A spring hingecomprising: a first hinge leaf; a second hinge leaf; a hinge pivotinterconnecting the first and second hinge leaves for pivoting betweenan open position and a closed position; a first spring support memberhaving a first end in pivotable engagement with the first hinge leaf; asecond spring support member having a first end in pivotable engagementwith the second hinge leaf; said hinge pivot being on one side of a linebetween the loci of pivotable engagement of the respective springsupport members with the hinge leaves in the closed position and not onthe same side of the line in the open position; means for pivotablyinterconnecting the first and second spring support members in scissorsfashion; and spring means interconnecting the second ends of therespective spring support members for urging the second ends towardseach other; and wherein the hinge leaves each comprise a window throughthe hinge leaf and a bearing tooth extending into the window, and eachspring support member comprises a hook extending through a respectiveone of said windows and a bearing surface in engagement with therespective bearing tooth.
 5. A spring hinge as defined in claim 4wherein each spring support member has a bearing arm extending over arespective hinge leaf and each bearing surface comprises an endextension of the bearing arm going through the respective window andeach hook comprises an extension beyond the bearing surface and fittingunder the bearing tooth.
 6. A spring hinge comprising: a first hingeleaf; a second hinge leaf; a hinge pivot interconnecting the first andsecond hinge leaves for pivoting between an open position and a closedposition; a window through the top of each hinge leaf, the pivot axis ofthe hinge pivot being on one side of a line between the windows with thehinge leaves in the closed position and not on the same side of the linewith the hinge leaves in the open position; pivot means extending downthrough each window, the pivot axes of the pivot means being parallel tothe pivot axis of the hinge pivot; spring means for exerting a biasingforce; means for transmitting the biasing force from the spring to thepivot means for exertion on the hinge leaves in a direction primarilybetween the pivot means, said spring means being at least partly belowthe windows; and means on the portion extending through each window forinhibiting removal of the pivot means from the respective window.
 7. Aspring hinge as defined in claim 6 wherein the means for transmittingand the spring means are an integral U-shaped member wherein the centerportion is elastically deflectable and the arms of the U aresubstantially rigid, the center portion being approximately normal tothe plane of the U as defined by the arms thereof.
 8. A spring hinge asdefined in claim 7 wherein the pivot means Comprises a hook on the endof each arm of the U-shaped member extending through the window.
 9. Aspring hinge as defined in claim 7 wherein the center portion of theU-shaped member has a U-shape extending a substantial distance beyondthe plane defined by the arms, and wherein the upper part of theU-shaped center portion is relatively narrower than the lower partthereof.
 10. A spring hinge as defined in claim 6 wherein the hingepivot is on the other side of the line between the loci of pivotableengagement with the hinge is in its open position.
 11. A spring hinge asdefined in claim 6 wherein the means for transmitting comprises: a pairof rigid U-shaped spring support members each comprising a bearing armconnected to the pivot means, a spring arm connected to the springmeans, and a bight portion interconnecting the bearing arm and thespring arm; and means interconnecting the spring support members alongthe bight portions thereof for pivoting about an axis parallel to thehinge pivot axis.
 12. A spring hinge as defined in claim 11 wherein thespring support members are molded plastic and the means for pivotingcomprises a flexible web of plastic integral with both spring supportmembers and extending therebetween.
 13. A spring hinge as defined inclaim 6 wherein the hinge leaves each comprise a window through thehinge leaf having a concave cylindrical bearing face and wherein themeans for transmitting the biasing force comprises a hook extendingthrough a respective one of said windows and a cylindrical bearingsurface in engagement with the respective bearing face.
 14. A springhinge as defined in claim 6 wherein the pivot means and the means forinhibiting removal comprise; a bearing surface extending through thewindow and a hook beneath a portion of the hinge leaf adjacent thewindow.
 15. A spring hinge as defined in claim 14 wherein each hingeleaf comprises a cylindrical bearing surface in the window and the pivotmeans comprises a cylindrical post engaging the cylindrical bearingsurface in the window.
 16. A spring hinge comprising: a first hingeleaf; a second hinge leaf; a hinge pivot interconnecting the first andsecond hinge leaves for pivoting between an open position and a closedposition; a window through the top of each hinge leaf, the pivot axis ofthe hinge pivot being on one side of a line between the windows with thehinge leaves in the closed position and not on the same side of the linewith the hinge leaves in the open position; pivot means extending downthrough each window, the pivot axes of the pivot means being parallel tothe pivot axis of the hinge pivot; spring means for exerting a biasingforce; means for transmitting the biasing force from the spring to thepivot means for exertion on the hinge leaves in a direction primarilybetween the pivot means, said spring means being at least partly belowthe window; said means for transmitting comprising: a pair of rigidU-shaped spring support members each comprising a bearing arm connectedto the pivot means, a spring arm connected to the spring means, and abight portion interconnecting the bearing arm and the spring arm, andmeans interconnecting the spring support members along the bightportions thereof for pivoting about an axis parallel to the hinge pivotaxis; and means for inhibiting removal of the pivot means from therespective window; and wherein one of the spring support memberscomprises a female socket and the other spring support member comprisesa male member engaging the female socket for forming the means forpivoting.
 17. A spring hinge as defined in claim 16 wherein the femalesocket comprises a concave cylinder facing the hinge pivot axis and themale member comprises a knife edge fitted into the cylinder.
 18. Aspring hinge comprising: a first hinge leaf; a second hinge leaf; ahinge pivot interconnecting the first and second hinGe leaves forpivoting between an open position and a closed position; a windowthrough the top of each hinge leaf, the pivot axis of the hinge pivotbeing on one side of a line between the windows with the hinge leaves inthe closed position and not on the same side of the line with the hingeleaves in the open position; pivot means extending down through eachwindow, the pivot axes of the pivot means being parallel to the pivotaxis of the hinge pivot; spring means for exerting a biasing force;means for transmitting the biasing force from the spring to the pivotmeans for exertion on the hinge leaves in a direction primarily betweenthe pivot means, said spring means being at least partly below thewindow; means for inhibiting removal of the pivot means from therespective window; the pivot means and the means for inhibiting removalcomprising a bearing surface extending through the window and a hookbeneath a portion of the hinge leaf adjacent the window; and whereineach hinge leaf comprises a bearing tooth in the window in engagementwith the bearing surface, the total included angle of the bearing toothand bearing surface being less than about 270*.
 19. A spring hinge asdefined in claim 6 wherein the means for transmitting and the springmeans are an integral C-shaped spring; and wherein the pivot meanscomprises a rivet through each window.
 20. A spring hinge for a pair ofbifold doors each having a door panel, a stile along each of the sideedges of the panel, and a rail along each end of the panel comprising;first and second hinge leaves, each hinge leaf comprising a leg forengaging a stile and an arm for fitting over the top of a rail andengaging therewith for connecting the rail and stile together; a hingepivot interconnecting the hinge leaves for pivoting between an openposition with rails in alignment and a closed position with rails sideby side; spring means below the top of the rail for exerting a biasingforce; and a pair of rigid U-shaped spring support members eachcomprising a bearing arm pivotally connected to a respective hinge leaf,a spring arm connected to the spring means, a bight portioninterconnecting the bearing arm and the spring arm, and meansinterconnecting the spring support members along the bight portionthereof for pivoting about an axis parallel to the hinge pivot axis forbiasing the leaves towards each other along a line lying on one side ofthe hinge pivot axis when in the closed position and on the other sidewhen in the open position.
 21. A spring hinge as defined in claim 20wherein the means for pivoting comprises a female cylindrical socket onone of the spring support members and a male knife edge on the otherspring support member engaging the female quasi-cylindrical socket, saidmale knife edge and female cylindrical socket extending parallel to thehinge pivot axis.
 22. A spring hinge as defined in claim 20 wherein thepivotal interconnection between the bearing arm and respective hingeleaf comprises a first bearing surface on the hinge leaf adjacent awindow through the hinge leaf, a second bearing surface on the bearingarm engaging the first bearing surface on the hinge leaf, and a hookbeneath a portion of the hinge leaf adjacent the window.
 23. A springhinge as defined in claim 22 wherein the first bearing surface comprisesa bearing tooth in engagement with the second bearing surface andwherein the total included angle of the bearing tooth and bearingsurface is less than about 270* .
 24. A spring hinge comprising a firsthinge leaf; a second hinge leaf; a hinge pivot interconnecting the firstand second hinge leaves for pivoting between a closed position and anopen position; a first bearing tooth on the first hinge leaf; a secondbearing tooth on the second hinge leaf, said hinge pivot being on oneside of a line between the bearing teeth on the two hinge leaves in theclosed position and not On the same side of the line in the openposition; a first spring support member having a first bearing face inengagement with the first bearing tooth; a second spring support memberhaving a second bearing face in engagement with the second bearingtooth; means for interconnecting said first and second spring supportmembers; means for retaining the first and second bearing faces inengagement with the first and second bearing teeth respectively; andmeans for urging the first bearing face towards the second bearing facein a direction along a line between the two bearing teeth.
 25. A springhinge as defined in claim 24 wherein the hinge pivot is on the otherside of the line between the loci of pivotable engagement when the hingeis in its open position.
 26. A spring hinge as defined in claim 25wherein the first and second bearing teeth each comprise an opening inthe respective hinge leaf and a projection extending into the openingfrom one side thereof, said projection pointing in a direction away fromthe hinge pivot; and the bearing faces each comprise a portion of thespring support member extending through the opening.
 27. A spring hingeas defined in claim 26 wherein the means for retaining comprises a tangon the end of each spring support member beyond the respective bearingface and extending along one face of the projection approximately in thedirection of the line between the bearing teeth.
 28. A spring hinge asdefined in claim 27 wherein the first and second spring support membersare opposite arms of a U-shaped member, the central portion of theU-shaped member being elastically bendable.
 29. A spring hinge asdefined in claim 27 wherein: each spring support member has a generallyU-shape with a bearing arm having the respective bearing face near theend thereof and a spring arm; the means for interconnecting the firstand second spring support members comprises a pivot having a pivot axisalong the bight of the U; and the means for urging comprises a tensionspring between spring arms.
 30. A spring hinge as defined in claim 25wherein the first and second spring support members, the means forinterconnecting and the means for urging collectively are an intergalU-shaped member having the bearing faces at the opposite ends thereofand wherein the central portion is elastically bendable.
 31. A springhinge as defined in claim 30 wherein each spring support member is onone side of its respective hinge leaf wherein the means for retainingcomprises: a tab on each end of the U-shaped member engageable with theside of the respective bearing tooth opposite from the side the springsupport member is on.
 32. A spring hinge as defined in claim 24 whereinthe first and second spring support members are each a molded plasticmember and the means for interconnecting the spring support memberscomprises a web of plastic integral with both of the spring supportmembers and extending parallel to the hinge pivot axis.
 33. A springhinge as defined in claim 24 wherein the spring support members aremolded plastic and the means for interconnecting comprises a flexibleweb of plastic integral with both spring support members and extendingtherebetween.
 34. A spring power pack comprising: a first rigid U-shapedspring support member; a second U-shaped spring support member, saidfirst and second spring support members each comprising a bearing arm, aspring arm and a bight portion interconnecting the bearing arm and thespring arm; means interconnecting the first and second spring supportmembers along the bight portions thereof for pivoting about an axisalong the bight portion; means on each of the pair of spring arms forconnecting a spring therebetween; and bearing means on each bearing armfor pivotally engaging a mating bearing surface, said bearing means onthe respective spring support members facing each other for exerting acompresSion force therewith.
 35. A spring power pack comprising: a firstrigid U-shaped spring support member; a second U-shaped spring supportmember, said first and second spring support members each comprising abearing arm, a spring arm and a bight portion interconnecting thebearing arm and the spring arm; means interconnecting the first andsecond spring support members along the bight portions thereof forpivoting about an axis along the bight portion comprising a femalequasi-cylindrical socket on one of the spring support members and a maleknife edge on the other spring support member engaging thequasi-cylindrical socket, said male knife edge and femalequasi-cylindrical socket extending parallel to the bight portions; meanson each of the pair of spring arms for connecting a spring therebetween;and bearing means on each bearing arm for pivotally engaging a matingbearing surface, said bearing means on the respective spring supportmembers facing each other for exerting a compression force therewith.36. A spring power pack as defined in claim 35 wherein the bearing meanscomprises a flat surface extending substantially normal to the bearingarm towards the spring arm and a hook portion extending beyond thebearing portion in a plane parallel to the plane of the bearing arms.37. A spring power pack ccomprising: a first rigid U-shaped springsupport member; a second U-shaped spring support member, said first andsecond spring support members each comprising a bearing arm, a springarm and a bight portion interconnecting the bearing arm and the springarm; means interconnecting the first and second spring support membersalong the bight portions thereof for pivoting about an axis along thebight portion; means on each of the pair of spring arms for connecting aspring therebetween; and bearing means on each bearing arm for pivotallyengaging a mating bearing surface comprising a flat surface extendingsubstantially normal to the bearing arm towards the spring arm and ahook portion extending beyond the bearing portion in a plane parallel tothe plane of the bearing arms, said bearing means on the respectivespring support members facing each other for exerting a compressionforce therewith.